Sheathed electric conductor



Dec. 22, 1953 J. v. MCBRIDE 2,663,755

SHEATHED ELECTRIC CONDUCTOR Filed Sept. 28, 1949 Imnentor (fOZl/Z V M cbm'cle (Ittomeg s Patented Dec. 22, 1953 SHEATHED ELECTRIC CONDUCTOR John V. McBride, Lebanon, Conn., assignor to The Plastic Wire & Cable Corporation, Jewett City, Conn., a corporation of Connecticut Application September 28, 1949, Serial No. 118,260

4 Claims. 1

This invention relates to sheathed electric conductcrs and an object is to provide n improved construction of insulated electric conductor for general purposes which can be installed substantially anywhere. Rural electrification installations, for example, are particularly severe and require a cable which is well insulated electrically, is well protected against mechanical injury and against moisture, acids, alkalis, oil, fungus, weather and sunlight and yet can be easily han died and readily bent to facilitate installation. 11 such installations it is also frequently necessary for the cable to withstand considerable tension, such, for example, as when the cable is required to span considerable distances without intervening supports, or when it is jerked and pulled around corners and through holes during installation. This calls for a cable having sufficient tensile strength to provide a greater margin of safety than is usually found in a cable which is also constructed to have the desired flexibility. Also, although cables have heretofore been provided with tension resistant cords or the like, they have been unsatisfactory because subject to rotting, or fungus growth, or objectionable for other reasons.

A feature of this invention is the provision of an electric cable having the necessary rugged insulation for prolonged service of the above type, constructed. and arranged to be so flexible as to permit ready installation thereof in and around sharp corners or wherever considerable bending of the cable is required, and which also has a greatly improved form of stress resisting means.

A further feature of the invention is the provision in an insulated electric cable of a strong tension resisting member formed of an inorganic, non-conducting material which is not subject to rotting, fungus growth and other objectionable features common to strands of the type usually employed in cable insulation such as cotton, jute or the like. The tension member is such as to provide maximum strength with minimum size, so that no increase in the overall dimensions of the cable envelope is produced.

A further feature is the provision of a multiconductor electric cable in which each individual conductor is slidable relatively to the insulating envelope. This feature contributes to the remarkable flexibility of the product permitting the cable to be bent as easily in the plane common to both conductors as in a direction at right angles thereto.

These and other objects and advantageous features are accomplished by the present invention.

In the accompanying drawings:

Figure l is a perspective view of a multi-conductor cable constructed in accordance with one embodiment of this invention.

Fig. 2 is a similar view of another embodiment.

Figs. 3 and i are sectional views of the cable shown in Figs. 1 and 2, respectively.

Fig. 5 is an elevation illustrating the easy flexibility of a cable constructed in accordance with the present invention.

Although the drawings illustrate different modifications of the invention incorporated in a two-conductor cable, it will be apparent that the invention is equally applicable to single conductor cables as well as to cables having more than two conductors, if desired.

In the form of the invention shown in Fig. 2 the electric conductors Ha, I20. are each surrounded by an individual insulating sheath 2|, preferably of the same material as the outer env-elope 22, such as vinyl chloride or a co-polymer. Each sheath 2| is surrounded by a protective, reinforcing and insulating layer of stress resisting strand 23 and the two conductors with their respective sheaths and stress resisting layers are enclosed in a substantially flat envelope 22, which also is preferably of vinyl chloride Or a co-polymer.

In order to avoid deterioration of the stress resisting strand due to rotting, fungus growth and other causes of deterioration heretofore encountered, I form the strand of inorganic, nonconducting material, preferably of fiber glass. Such material provides the necessary strength and flexibility with a minimum size of strand so that the outside dimension of the insulating envelope is not increased by the presence of the strand. This is of especial advantagein a flat cable having a substantially flat envelope, as no increase in the outside dimension of the envelope is required. Fiber glass also has the advantage of being a good electrical insulator so that the presence of the strand does not decrease the insulation provided by the envelope between the electric conductors.

In this embodiment, each conductor is first supplied with the extruded sheath 2! by running through a suitable extruding die. Then the layer of stress resisting fiber glass is applied around each sheath, and such covered wires and sheaths are then fed through a suitable extruding machine to have the envelope 22 applied thereto.

In this embodiment of the invention it will be found that each conductor and its surrounding sheath is slidable relatively to the outer envelope 22, the intervening layer of fiber glass reducing the friction between each sheath and the surrounding envelope, so that this form of cable is as easily flexible in the plane of the conductors as in any other plane as is clear from Fig. 5. With the fiber glass surrounding the conductors as in this form of theinvention theiinsulating; envelope is also reinforced against clamping pressures as might be encountered in fastening the cable in position, and against serious defermation due to high pressures at. elevatedtem: peratures.

As illustrated in Figs. 2 and 4;,th'e;oonchictors: l 5?), i272 are enclosed in separateisheaths=25 similar to the 2! each sheath' having-an=iden=- tifying or indicating characteristi such for; example as a distinctive contrasting color. The color of one sheath may be the same asthe envelope 2% as long as the other sheath is of a contrasting color.. ln-this;embodiment arstressx resisting cord itboffiber glassis employed-and extends longitudinally of the cable: parallel, to the conductors and, as illustrated, is substantially midway between them.

ltwill be seen that the-present invention prc vides an electric cable which can be used in practically any typeof installation; which will-easily; absorb the tensile stressesimpc-sed'on it and yet which is so flexible as to permit ready-installations around sharp corners and the like.-

Although the drawing shows theinventionaanplied to. cable having solid conductors,.it.willileev understood that the, invention: is equally: well, adapted to cables havingany other form-offcone ductonstranded or; otherwise.

The invention can be variouslyniediiledi and;

layer of fiber glass surrounding-each c fi' saidgconx-- doctors {within said envelope and enclosed. theree by..

2. An electric cable oi indefinite-length corprising parallel conductors, an: extruded; fiexibl insulating sheath of homogeneous--thermoplastic material enclosing each conductcr,;an. extruded; flexible insulating envelope of, homogeneous thermoplastic material, encircling and; slidablyr engaging and enclosing each-ci saidsheaths', said; envelope being free or" interconnection with said: sheaths whereby to facilitate flex-ingot thecablein theplane of said conductors:andsaidenvelope,

l providing a large mass of insulation extending between said sheaths for the full width of the sheathed conductors, and a stress resisting member of fiber glass material enclosed within said envelope and extending longitudinally through said mass of insulation parallel to said conductors.

3. An electriccahle of indefinitelen'gthcompris ing parallel'conductors, anextruded, flexible insulating sheath of homogeneous vinyl chloride enclosing each conductor, an extruded, flexible insulating envelopeof homogeneous vinyl chloride encircling and enclosing each of said sheaths and being slidable thereover, said envelope being free of 'any interconneeticn with said sheaths and prov'idin'g a largemass'of insulation extending be tween: said sheaths: for the full width of the sheathed conductors, whereby to facilitate sliding of the envelope on the sheaths incident to the flexing of the cable in the plane of said conductors,- and? a stress resisting member of fiber glass enclosed within saii envelope and extending-loingitudinally therethrough,

4e- An elect to cableof inclefinitelength com-- prising parallel conductors, an extruded; flexible sheath of homogeneous vinyl chloride enclosing each conductor; a layer of inorganicnon-con ducting stress resisting fiber" glass surrounding each-sheath; and an extruded; flexible envelope of homogeneous vinyl chloride surrounding and slid ably engaging and enclosing each of" said files" glass layers; wherebyto-facilitate flexing of cable in the plane of said conductors; said envelopeforming a solid mass :between' said sheaths forthe full width of the'sheathed conductors-to maintain said conductors in predetermined spaced relation;

JGHNV. MCBRIDE:

References ones in the file. of. thi'slpabent'.

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